


Well, It Must Be Chemical

by Maeniac



Category: Sonic the Hedgehog (Video Games), Sonic the Hedgehog - All Media Types
Genre: Action, Canon-Typical Violence, Cuddling & Snuggling, Eggman-Typical Scheming, Fluff and Angst, Getting Together, Happy Ending, Hurt/Comfort, Implied/Referenced PTSD Flashback, Injury Recovery, M/M, Needles/Syringes, Nightmares, Other Additional Tags to Be Added, Post-Shadow the Hedgehog (2005), Post-Sonic Heroes, Post-Traumatic Stress Disorder - PTSD, Rated teen for swearing, Slow Burn, Sonic Says Fuck
Language: English
Status: In-Progress
Published: 2021-02-02
Updated: 2021-02-14
Packaged: 2021-03-13 15:00:28
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 3
Words: 8,869
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/29155467
Author URL: https://archiveofourown.org/users/Maeniac/pseuds/Maeniac
Summary: Before them, the entrance to the warehouse yawned, dark and impenetrable. They paused for a moment, ears pricked and listening."One last thing," Sonic said, when nothing had happened. "This is a trap isn't it?"Shadow snorted. "Obviously."Sonic grinned, clapping Shadow on the back. "Perfect. Let's go!"After saving the world from the Black Arms and clearing his name, Shadow took his well-earned place among the heroes of Mobius. A year on, and Sonic has grown to count on him as a strong and reliable teammate. He's pretty sure he could even call them friends.That is, until a routine infiltration goes wrong. Shadow falls victim to one of Doctor Eggman's sinister creations -- a serum he claims will unleash Shadow's true destructive nature. With their friendship on the line, Sonic needs to find a way to stop Eggman's latest scheme, and confront the uncomfortable truth: that maybe he didn't understand his relationship with Shadow as well as he thought.
Relationships: Shadow the Hedgehog/Sonic the Hedgehog
Comments: 52
Kudos: 113





	1. Chapter 1

**Author's Note:**

> Welcome! At the time of posting, this story has been on my mind for a whole year now and I have 27K already written. I fully expect that word count to double by the end of this. The update schedule is likely to be posting chapters once the one after it has been edited. I hope you guys enjoy coming along with me for the ride!
> 
> One last thing of note before the chapter: Sonic gets pretty beat up. Like, opening cutscene to Shadow the Hedgehog levels of beat up. But I promise he's fine in the end.

"You're late."

Slowing from his sprint, Sonic's greeting turned into a rebuttal halfway out of his mouth. "Wh- I am _not_. I said I would be here in five minutes, tops."

"And yet, it's been five and a half minutes since you said those words." Shadow's head turned away, as if in shame. He _tsked_. "Sloppy."

Sonic rolled his eyes. "If you're done scolding me for my tardiness, Headmistress," he said with a pointed elbow to Shadow's side. "Would you mind filling me in?"

There came a mutter of " _Headmistress indeed_ ," before Shadow said, "This way."

Reports had come in of suspicious activity in the western corner of Spiralwood Forest. Felled trees and burrowed holes that, when checked with the proper administration, had never been authorized. But illegal logging and mining operations were just the tip of the iceberg. There'd been sightings of shadowed figures, crawling through the forest with crates of supplies like ants bringing their foraging back to the nest.

"This has Dr. Eggman written all over it," Sonic said, putting the pieces together. "It's been too quiet lately; he must be preparing something big."

"My thoughts precisely," Shadow agreed. 

"And this location that we're heading to?"

"Supposedly, a warehouse with sporadic activity. Of course, there's no definitive proof that the one behind this operation is, in fact, the good Doctor."

"So the plan is to go in, find our proof, and take out his next evil scheme while it's still a work in progress." Sonic side-eyed him. "And you wanted _my_ help with this because...?"

"Our presence was requested by one of the locals," Shadow explained, eyes forward, brushing aside the trailing undergrowth in his path. "They had quite the scare running into a loading party in the middle of the night. It makes sense that they'd want some form of reassurance for a problem this close to home."

Sonic's curiosity didn't abate. "What about your teammates?"

"Rouge and Omega left on a mission not too long ago -- one that requires relatively deep cover and with a narrow window of opportunity. They were making their preparations at about the same time this intel came in, so the two of them left it with me to handle." At this, Shadow's business-like demeanor slipped, and for a moment he looked disappointed. Then, with a shake of his head, it was gone.

"Besides," Shadow continued, "between the two of us, we stand the best chance of getting in and out with little notice." He met Sonic's gaze and raised his brow in challenge. "You _are_ capable of stealth, aren't you? I had my doubts, but if you want to prove me _right_..."

 _Damn_ Shadow for knowing exactly how to ruffle his quills.

They soon emerged into a man-made clearing, made all the more obvious by the remnants of tree stumps and heavy tire tracks gouged into the soft earth. Ahead of them stood the warehouse, a dull and innocuous building from the outside. It backed into the side of a cliff, the ground rising steeply and casting a looming shadow across the whole clearing. There would be no sneaking in from behind this time. Only the front doors awaited them.

Shadow approached and silently swung the doors open wide. Before them, the entrance to the warehouse yawned, dark and impenetrable. They paused for a moment, ears pricked and listening.

"One last thing," Sonic said, when nothing had happened. "This is a trap isn't it?"

Shadow snorted. "Obviously."

Sonic grinned, clapping Shadow on the back. "Perfect. Let's go!"

They stepped over the threshold, and the door shut behind them without a sound.

* * *

It was a trap, because of course it was. They were caught off guard, because of course they were.

And it went from bad to worse, because _of course it did_.

It started in the middle of their search. Sweeping the place room by room, they scoured every nook and cranny, trying to find _something_. A death ray, a battle mech, a conveniently labelled big red button -- any sign of a certain evil scientist. But they kept coming up empty. All they'd discovered so far were a handful of open, unmarked crates, their contents long gone.

Sonic frowned. None of it was adding up.

Then, while they were making their way quick and silent down yet another corridor, Shadow slowed. He threw an arm out in front of Sonic to halt him.

At his questioning look, Shadow whispered, “Listen.”

Silence, at first. Then, faintly, the slow scrape of metal against concrete.

They exchanged glances.

“Stay close,” Shadow continued, so quiet Sonic could barely hear him, despite the two of them huddling together. “We’re continuing forward -- with _caution_ ,” he added pointedly.

Sonic muttered a petulant, “ _Duh_ ,” even as Shadow turned his back to him once more.

They crept further along, on high alert, just _waiting_ for an enemy to appear.

It was agony for Sonic to move so slowly. He had half a mind to just shove Shadow to one side and forge ahead on his own -- if Eggman was up to something, he wanted to _know,_ damn it -- but he kept his thoughts to himself. Loathe as he was to admit it out loud, Shadow had far more experience with infiltration missions. Sonic would follow his lead on this one.

Just a meter from the room where he was sure the sound was coming from, it stopped. Shadow only paused for a moment, before flattening himself against one side of the doorway. Ever so carefully, he peeked out.

Patience running thin, Sonic stretched up on his toes, bracing a hand on his back to peer over Shadow's shoulder. The room was empty.

With a huff and a mean look in his direction, Shadow stepped further inside, deliberately out of his grip. "There's nothing here," he said, no longer at a whisper.

"I can see that. What, are you saying it's _my_ fault?"

Shadow opened his mouth to reply, but he never got the chance to hear it. At that exact moment, Sonic had followed him across the threshold, and a heavy blast door slammed down behind him.

The two whipped around in alarm. Moments later, a mechanical hiss filled the room, as the walls began to close in around them.

Sonic turned to his partner, urgency clear in every word. "Shadow! Tell me you brought your chaos emerald with you!"

But his rival only grimaced. Sonic's eyes roved the increasingly shrinking room, searching desperately for an escape. But what could they use? All he saw was more featureless, unyielding concrete.

Sonic curled up, building up a burst of speed before ricocheting all around the room. Nothing. He tried spin-dashing directly into the encroaching walls. Hardly a scratch. Helpless with frustration, he kicked out where the door had once been, but all it did was send pain shooting up his foot. Shadow seemed to be having the same poor luck as him. He grit his teeth.

In a last ditch attempt, Sonic put his shoulder against the wall and pushed. His feet slid back, finding no purchase against the smooth stone.

"Okay, that's it!" he called over to Shadow, switching to press his whole back up against the wall. "If you've thought up a plan to get us out of here, I'd _love_ to hear it!"

"I'm _trying_ ," Shadow hissed from the opposite side of the room, just a stone's throw away now. 

Sonic squeezed his eyes shut tight and -- one more time -- _heaved_.

Everything stopped.

The two of them stood stock still.

"Did-" Sonic panted, breathless, hardly daring to hope- "Did that work?"

Shadow surveyed the room, still wary. Still on his guard. "No."

From all around them the walls opened up, and a veritable army of robots came pouring in. They all bore the familiar lifeless grins of every Eggbot, but something about them was different, an odd sheen to their carapaces. Instinctually, Sonic and Shadow retreated to the center of the room. They stood back to back, facing out into a sea of gleaming eyes.

"So," Sonic said, attempting to keep his voice light. "Definitely Eggman, then. You up for knocking a few heads together?"

Shadow's only reply was a growl before he launched himself into the fray.

Sonic wasted no time following his lead. He singled out the nearest bot and released a flurry of kicks, every single one of them blocked by its thickly-plated arms. Another came in from the side and tried to grab him. He dodged back, side-stepping another swipe, and another. Everywhere he moved, there was always another set of hands ready to catch him, another pair of eyes watching, waiting for him to slip up.

Sweat began to drip down his neck. With so little room, Sonic was barely managing to dodge the attacks coming in from every side, and none of the blows he landed had any effect. It was quickly becoming apparent that he needed to think of something, and _fast_.

With one strong push of his legs, Sonic leapt above the crowd. But there was no time to enjoy the relief of freedom. He kicked off the ceiling, hoping to build up enough momentum to do some real damage. Rocketing back down, Sonic curled up just before impact-

And was met with a horrible stabbing pain as the quills on his back splintered.

Before he could retreat, a cold hand clamped around his leg, holding him bodily off the ground. His vision flipped on its head. With a snarl, Sonic lashed out -- he did _not_ like when people grabbed his legs to keep him from running -- and punched the bot holding him square in the knee cap.

He had to choke back his scream. What the heck were these things _made_ of?

Distracted and immobile as he was, Sonic could do nothing as he was raised up by his leg and clocked in the face by another bot. The blow knocked him out of its grip, sending him tumbling to the floor. He struggled to get up. His vision filled with spots, ears ringing. 

Ahead of him, a blur of movement resolved itself into Shadow, still fighting tooth and nail. The bots were surrounding him, tightening the ring until there was nowhere to escape, hands grasping for him. A moment later, sound filtered back in.

" _Unhand_ me, you repulsive-"

"Shadow!" Sonic cried, staggering to his feet, but he was _slow._ Two bots grabbed either arm, pulling them behind his back, until all he could do was struggle and strain forward. "Shadow! Hang on, I-"

Pain cracked through his skull -- the kind of pain that reminded him of wiping out on loop-de-loops and plummeting head first towards the ground. He swayed, the room listed to one side, and then he knew no more.

* * *

Sonic woke up to a dull throbbing behind his eyes and the iron tang of blood in his mouth. He kept his eyes closed for now, listening carefully for signs of someone else in the room. All he could hear was another set of soft breaths, deep and slow. Probably unconscious.

He took stock of his injuries. Wriggling his toes showed that his legs seemed to be working just fine, but attempting the same with his hands brought on a wave of pins and needles. He winced. Whoever restrained him had strung his arms up above his head. Running his tongue carefully over his teeth, it seemed none had been knocked loose. There was a cut on the inside of his left cheek, but it didn't feel serious. He must have accidentally bit down some time during the fight.

The fight -- Eggman's robots -- _Shadow!_

Sonic's eyes snapped open.

It took him a moment to adjust to the stark lighting, but soon he was met with a small, sparsely furnished room, barely wider than the one they had been trapped in before. Directly across from him, lay an operating table, its occupant a familiar bundle of black and red fur.

A pit opened up in Sonic's stomach. Shadow's arms and legs had been bolted down to the table and -- was that a _gag_ over his mouth? Eyes darting around frantically, Sonic checked his friend over, but it seemed he was relatively unharmed. There were a few bruises and scrapes here and there, but seemingly nothing life threatening. In fact, Shadow's face looked almost... peaceful, unmarred by his characteristic scowl. Sonic could almost convince himself that they'd been taken to a hospital -- were it not for their shackles and the giant robotic arm looming over Shadow's prone form. He had a bad feeling about all this.

"Shadow," he croaked. "Bud, come on, talk to me."

There came a low groan, and after a moment Shadow's eyelids fluttered. Sonic sucked in a sharp breath, the smell of disinfectant thick in the air. 

But there was little time to rejoice in Shadow's awakening. The adjacent wall -- previously dark and blank -- now lit up in full colour, as Eggman's laughter filled the room.

"Rise and shine, vermin," the projection announced cheerily. "And _welcome_... to your demise!"

Sonic mustered the energy to roll his eyes. "What is it this time, Eggman?"

He clicked his tongue. "Looks like someone woke up on the wrong side of the prison cell. Ah, but not to worry, you won't be tied up for much longer..."

Sonic narrowed his eyes. On the other side of the room, Shadow shifted restlessly, testing the limits of his restraints. They held fast.

"You see, I had the most interesting train of thought the other day. Here I am, the perfect mastermind to usher the world into a new and glorious era," he mused, before his voice turned steely with barely concealed anger, "--if it weren't for one _persistent_ blue thorn in my side, constantly getting in the way!"

He smirked at that. "Can't be much of a genius if all it takes is a hedgehog to ruin your plans."

Eggman's glare filled the screen. "Zip it, you overgrown prickly pear, or I'll gag you, too. Now, where was I? Ah, yes: it's been especially troublesome ever since Shadow joined your little--" his lip curled-- " _band of heroes_. I'm still terribly disappointed in you, Shadow. Are you quite sure I can't change your mind?"

Despite the lower half of his face being covered, Shadow was still able to give him an impressively dirty look.

"A pity," the Doctor said, but his grin had returned. "It seems you've left me no choice."

On the other side of the room, the robotic arm suddenly whirred to life. It swivelled and extended, positioning itself directly over Shadow -- poised, as if to strike. Meanwhile, Eggman continued his monologue.

"And what is one to do when faced with two _pests?_ Well, the answer came to me, as if sent by the Fates themselves, absolute genius in its simplicity --" He paused dramatically, practically beaming. "You'll just have to get rid of each other _for_ me."

Sonic burst into disparaging laughter. "I think you might have a screw loose, Egghead. Last I checked, Shadow and I were on the same team."

"The _name_ is Dr. Robotnik," he spat, face purpling with rage, before the expression was quickly wiped clean. His next words turned soft and dangerous. "And who said you were?"

Sonic blinked.

Eggman sighed. "It sounds like such a _perfect_ story, doesn't it? The once-villain, now redeemed and praised as one of the heroes." He chortled. "Come off it! Shadow was made for one purpose and one purpose only: to _destroy_ anything standing in his way! Including you."

"You're wrong, Eggman. You don't know anything about us."

"Care to wager your life on that, hedgehog?"

Sonic bared his teeth. "Shadow and I are _friends."_

"Oh, I'm sure you think so. I must say, it's all been a rather impressive charade. I can't imagine how painful it's been to put up with your constant obnoxious chattering, to watch adoring fans _fawn_ over their perfect little hero, to always be overlooked as _second best."_ The Doctor's dark, beady eyes bored into him. He felt as if there was a pound of lead sitting in his gut. "The resentment must be _eating him alive._ But I have a way to fix all that."

A sheath pulled back at the end of the robotic arm, revealing a glass syringe filled with a noxious purple liquid. Sonic froze, unable to look away.

"Behold, Sonic, my latest creation: Project Nemesis," he declared, voice brimming with pride. "I've devised a chemical concoction to amplify the most primal emotions and render one's impulse control inert. That is to say..."

The tip of the needle gleamed, sharp and dangerous.

"There will be _nothing_ to stop Shadow from fulfilling his heart's deepest, most selfish desire."

Shadow's eyes widened in terror, and then he redoubled his efforts to break free. The arm slowly began to lower.

"Come now, Shadow," the Doctor cooed. "There's no need to fear. Think how much this will _help_ you."

Sonic swallowed the lump in his throat. "Shadow, tell me it's not true," he pleaded.

But Shadow wouldn't meet his eyes anymore. He huffed and growled in exertion as he thrashed, ears pinned flat to his head. He looked like a cornered wild animal.

Another bout of cackling rang out. "My _goodness_ Sonic, what a fantastic expression that is. Oh, but _do_ save it for when the cameras start rolling. I want to broadcast your defeat at Shadow's hands to _every one_ of your little friends."

Sonic watched, horrified, as the needle embedded itself into Shadow's arm. A muffled scream sounded through the gag. He strained forward, even knowing full well that he couldn't do _anything_ to stop it.

_"Shadow!"_

The vial emptied. Sonic felt his heart stop, breath caught in his throat. The syringe retracted itself, drawing back up into the robotic arm as if it had never been.

"I'll leave you two alone to... sort out your differences." He laughed again. "I look forward to seeing you later, Shadow. Do me proud."

"... And have fun."

The screen went dark. There was a beat of silence, and then an echoing clang as both sets of cuffs released them.


	2. Chapter 2

**Notes for the Chapter:**

> Double update because as much as I love a cliff-hanger, the start of this story doesn't feel complete without it. Enjoy!

Sonic barely caught himself as he fell to the ground. He grit his teeth against the wave of dizziness, the pins and needles prickling through his arms as the feeling returned to them. When they'd subsided, he pushed himself to his feet, and looked for his friend.

 _If you can even call him that_ , a small voice in his mind whispered. He shook it off.

Shadow sat huddled in the furthest corner, clutching at his head. Sonic stumbled towards him. No matter how Shadow may or may not feel about him -- he needed help.

As he grew closer, it was with no small amount of alarm that he noticed the tremor in Shadow's limbs.

"Shadow, are you okay?"

At first, he almost thought Shadow hadn't heard him. But then-

"... Stay back."

"What?" Sonic stopped, confused. He was so close now, close enough to touch. He reached out a hand.

Shadow's head snapped up and he roared, "Get _away!_ "

Sonic couldn't hold in his gasp. Shadow's eyes were -- strange. His pupils kept fluctuating, growing and shrinking rapidly despite the consistent light. And his face... Sonic was sure he'd never seen Shadow look so panicked.

He searched for something to say. "I just want to help."

"If you have any sense, you'll stay as far away from me as you can," Shadow replied through clenched teeth. His chest rose and fell quickly, breath shallow.

"And why should I?" Sonic demanded. It couldn't be true, could it? There was no way Shadow could hate him as much as the Doctor insisted, no way their friendship could all be a lie.

There was no way Shadow would want to _kill_ him... right?

But Shadow curled up further, bowing his head so he wouldn't have to meet Sonic's eyes. Through the shivers wracking his body, he whispered, "I don't know what I'll do."

Sonic's blood ran cold. He took a step back. Slowly, he shook his head, until the dizziness threatened to overwhelm him again.

"No. No, we'll find a way out of this. We have to try."

"I don't know how much time I have--"

"Don't _do_ this, Shadow!" he shouted, hands tightening into fists at his sides. "I'm your friend. I'm not gonna just _leave_ you here like this!"

Shadow met his eyes. "Then you're a fool," he said, before doubling over as the serum finally consumed him.

It happened in an instant. Something in Shadow's stance _changed._ It became more threatening, almost predatory. His head raised to scent the air, gaze searching the room as if seeing it for the first time.

Shadow's eyes finally locked onto Sonic. And he saw the pupils blown so wide that the red of his irises was barely visible. A low, rumbling growl picked up.

"Hey there, buddy," Sonic said, his smile stiff on his face. "Remember me?"

There was no reply. In one fluid motion, Shadow rose to his feet and began deliberately stalking towards him. His gaze never wavered.

Distantly, Sonic felt himself shy away. It was as if someone else had control of his body. For the first time since they'd arrived at the warehouse, fear's icy claws took root in his chest.

He stumbled as his back hit the wall. There was nowhere left to go, and Shadow was right in front of him now. That growl continued, lip curled back to reveal a pointed fang. Those dark eyes were a bottomless void, pulling him in.

Sonic struggled to keep his tone light-hearted. "Come on, man, cut it out... You're starting to scare me."

Shadow frowned. His footsteps came to a halt, mere inches away. They were so close that Sonic wondered if he could hear his heart drumming in his chest. He tried not to blink.

A hand came up to reach for him. Sonic flinched away, half-expecting his throat to get torn out at any moment despite himself.

There was a pause. He couldn't hear anything over the blood roaring in his ears. Had the growling stopped?

But then, something brushed against his cheek ever so gently, barely a whisper across his skin. He cracked an eye open, and it was just... Shadow. Still standing there, staring intently at him. The pad of his thumb carefully swiped under his left eye. There was a new look on his face, one Sonic had never seen on him before.

It was... concerned?

The thumb pressed down, testing, and Sonic felt an answering sting at the pressure. All at once, the pieces clicked together in his mind, but the big picture still didn't make any sense to him.

He brought up his own hand to where Shadow was prodding his black eye, fingers curling loosely around his wrist. Shadow looked down at the contact, then back at him.

"I'm okay," Sonic said softly.

Shadow seemed to relax at that, the furrow in his brow easing. He took his hand away. Sonic's skin tingled where he'd touched him, but he forced the sensation out of his mind. Now was not the time. 

Pushing himself off the wall, he started, "We should try to get out of here. I- whoa!"

In trying to support himself, he lost his balance, head-spinning, but Shadow was quick to catch him. Those strong arms held him steady. Another noise left him -- a strange, resonant warbling. Sonic had no idea what it meant, but judging from his expression, Shadow was worried for him. Again.

It was still weird to think about.

"It's fine," Sonic assured, fumbling to pat Shadow on the shoulder. "It's just this dang head injury slowing me down. But we _really_ need to get moving." He didn't want to wait around for more of those indestructible bots to come in and check on them.

Shadow shifted, and for a moment Sonic thought he was about to let go. But then his legs were being swept off the ground as he was lifted securely into a princess carry. He spluttered, face heating up.

"Hey, hey! What do you think you're doing? I can walk just fine, thanks! And did you have to pick me up like _this?_ Are you even listening to me? _Shadow."_

But his friend paid him no mind. Instead, he walked calmly over to the screen where Doctor Eggman's face had once been, now inactive.

Shadow's mouth pulled up into a vicious smirk. He took a moment to adjust his hold on Sonic, and then lashed out with his free hand. A crash echoed throughout the empty room, followed by the shriek of tearing metal as Shadow ripped a hole open in the wall. With his bare claws. In a matter of _seconds._

Sonic's brain struggled to process as they shuffled through the gap and out into another part of the warehouse. It appeared to be a maintenance tunnel. Shadow picked a direction, seemingly at random, and kept moving. 

When he finally found the capacity for words again, Sonic couldn't keep the incredulity out of his voice if he tried.

"Did you just punch through a fucking _wall?"_

No answer. He was beginning to resign himself to the fact that Shadow wasn't going to talk, but his thoughts were interrupted when an alarm blared. Their escape had not gone unnoticed.

Shadow burst into a sprint, zipping down the hall. Lights flashed orange and yellow as they whipped past, until they came to an abrupt halt at the next turn.

The room they found themselves in was the largest they'd seen so far, and _teeming_ with robots. They bustled about, patrolling the upper walkways and attending to the assembly lines within. Upon their entrance, however, all production came to a standstill. Every single bot had turned to them, their eyes glittering.

Sonic wrapped his arms around Shadow's neck.

"If you drop me, I'm gonna kick your ass later."

Shadow's grip on him tightened in response.

Overhead, a speaker crackled to life as Doctor Eggman gave the order to his waiting soldiers.

_"What are you standing around for? Get them!"_

The robots charged, but this time, Shadow was ready for them.

At least ten swarmed the entrance, forcing him to dodge or be captured once more. But now, the odds had shifted in their favour. Instead of being confined to close-quarters, there was more room for Shadow to swerve and double back, always careful to keep out of reach. He was practically _dancing_ around them, as Sonic hung on for dear life.

Soon, he had broken through the first wave. More tried to rush them. With a few well-timed spins, Shadow had them crashing into crates, scaffolding, even each other. But he couldn't keep track of them all.

They crowded him back up against one of the conveyor belts, forcing him to work double time just to fend them off.

Sonic saw one bot get in too close, and yelled, "Look out!"

It was just enough. With a jolt, Shadow sprang back. Sonic felt the robot's cold fingers brush his fur, but -- ultimately -- close around thin air. They landed on the conveyor belt, groaning at the extra weight, and Shadow wasted no time racing down its track. Parts scattered in their wake.

They were closing in on the exit now. Sonic could feel the adrenaline zinging through his blood, a wild grin stretching his cheeks despite the dire circumstances.

_Just a little further!_

Unfortunately, some of the bots had grown wise. Three had already climbed onto the conveyor, blocking their path, and more still were on their way.

Shadow narrowed his eyes at them, but his stride never faltered. Sonic held his breath as the two of them rushed forward. When they were only a hand's breadth away, Shadow kicked out, launching himself and Sonic off of the lead bot and over the side. Right on top of the gathered throng, clamouring for a boost.

The nearest looked up -- just in time for Shadow's rocket-powered sole to slam into its face.

It overbalanced, crashing to the floor, but Shadow had already moved on to the next. And the one after that. They leapt across the mass, completely untouchable. Sonic whooped and laughed with every curb-stomped bucket of bolts

At last, they reached the other end of the room. Shadow hopped down, tucking into a roll with practiced ease in spite of the extra cargo. In mere moments, they were through the doors and leaving Eggman's machines in the dust.

The warehouse passed by in a blur after that. Sonic caught glimpses of more cavernous rooms, strange machinery of mystifying purpose and sprawling pipes, before Shadow came across an emergency staircase. He wasted no time rocketing up the handrail in a shower of sparks. They didn't encounter much more security, and what little there was just couldn't keep up. At some point, Shadow must have recognized where they were within the labyrinth. He picked up the pace. Moments later, they were back in those winding hallways, and then-

The front doors flew off their hinges, sunlight flooded in, and Sonic took his first breath of fresh air in what felt like _days._

They continued through the forest, back towards town. As their prison grew smaller and smaller behind them, Sonic hoisted himself up to look over Shadow's shoulder. There was nothing left but green.

"Can't see anymore bots" he said, relaxing back into Shadow's hold. "I don't think they're following us. Looks like we're in the clear."

But Shadow didn't slow down, nor did he ease his grip. Sonic frowned. Now that they weren't in immediate danger, his previous worry over Shadow's condition began to creep in once more. Just how much had that serum affected him?

He glanced around them again. Another burning question came to mind.

"Hey, Shadow? Where are we going?"

And to Sonic's utter astonishment, he replied, "Home."

* * *

It was late afternoon by the time they arrived at Sonic and Tails' house.

Sonic liked to think he lived quite modestly in spite of his fame. The house was two storeys, all rustic wood, white-framed windows and shingled rooves. A scattered stone path led up to the front door. He couldn't say much for the garden -- neither he nor Tails had an especially green thumb -- but the lush grass and wild flowers surrounding their front step was pretty enough. Off to the left, the ground floor jutted out, housing what was arguably Tails' favourite room in the entire house.

"Tails is probably in the garage," he told Shadow as they approached, pointing towards it. "We can go in through the back."

Shadow silently obliged. Despite Sonic's best efforts, he'd been unsuccessful in convincing Shadow to speak again, no matter how much he'd pestered him. The near-absolute silence was starting to aggravate him.

The roller door had been left wide open, allowing the day's pleasant breeze to sweep through Tails' workshop. Shelves of all manner of shapes, sizes and transport capabilities lined the room, drawers opened haphazardly to reveal their contents. Tools hung from steel brackets on every wall. Taking up the center of the space was the workbench. It was two square meters of polished wood, nicks and scratches etched into its surface from years of frequent use. There were all sorts of gadgets arranged on it, everything Tails would need for his latest project within easy reach.

His adopted brother was hard at work, head bent over the desk, back towards them. Tails' ear flicked at the sound of Shadow's footsteps tapping across the concrete floor. He started talking before he'd even turned around.

"Hey, you're back kinda late. What took you so-"

His tool box crashed to the floor.

"Sonic! What _happened?"_

Sonic waved, grinning sheepishly from Shadow's arms.

"Hey, Tails," he greeted. "Mission didn't go so well."


	3. Chapter 3

**Notes for the Chapter:**

> Happy Valentines Day! This one's for the gays.
> 
> (Also heads up, this chapter contains needles again as well as an implied ptsd flashback. Stay safe!)

The story came out while Tails dug up the first-aid kit stashed in the corner of the garage. He listened with wide eyes as Sonic recounted infiltrating the warehouse, their imprisonment, and Eggman's apparent scheme. With a glance towards Shadow, Sonic decided to skim over what happened immediately after the injection. He didn't know what to make of it himself.

Now, Sonic sat in Tails' wheelie chair, patiently enduring a very serious medical examination.

"Have you lost consciousness at all since you woke up?" Tails asked, disinfecting the scrapes across the back of his knuckles.

Sonic winced at the sting. "Nope."

The wounds now sterilized, Tails grabbed a roll of bandages and began wrapping them around his hand.

"Any nausea or vomiting?"

He held in a sigh. Tails had a bad tendency to fuss over the smallest injuries. "Nuh-uh."

"Has any fluid -- blood or otherwise -- come from your ears or nose?"

"Ew, gross." Sonic wrinkled his nose. _"No._ I keep telling you -- I'm _fine."_

Tails folded his arms with a huff. "Concussions are serious business, Mister, and you know it."

"It's not that serious! You and Shadow--" he gestured to where the hedgehog had been silently hovering at his side for the past ten minutes-- "are overreacting. I've just got a headache and my balance is a little messed up. That's practically nothing."

Tails squinted at him dubiously. His foot tapped in agitation. For a long moment, neither of them spoke, locked in a stalemate.

But eventually, Tails heaved a sigh.

"Fine," he relented. "I'll give you some painkillers. But if that headache doesn't go away in a few hours -- or it gets worse, or you pass out again, or throw up, or--"

Sonic held his free hand up in surrender. "I get it, I get it. If anything happens we're going straight to the hospital. I promise."

With a satisfied nod, his little brother tied off the bandages. "I'll fetch those painkillers for you now." He glanced at Sonic's face and grimaced. "And an ice-pack."

"Thanks, man. I appreciate you looking out for me," Sonic replied, ruffling the fur between Tails' ears. He got a playful swat in return before he trotted out of the room, twin-tails swishing behind him.

Sonic leaned back in his chair, staring up at the ceiling. Chaos, he was tired. This day had gone on forever. His eyes slipped closed, as he tried to ignore all his aches and pains and just... _rest._ At least for a moment.

His mind drifted. From beyond the garage's open door, he could hear birds twittering outside. The scent of pollen and last night's rainfall filled his lungs. He breathed it in.

At his right, shoes scuffed against the floor, shifting restlessly. He heard a single step, a whisper of movement, and then there was that same light touch to his face.

Sonic's eyes opened. He sucked in a breath, surprised to find Shadow so close again, those dark eyes like bottomless pools searching his face. This time, however, he didn't linger on Sonic's bruise. His hand slipped down to his neck, fingers resting over his pulse. Sonic couldn't bring himself to move. He held his breath, heart thudding, waiting to see what Shadow might do next.

At that moment, Tails re-entered the room, double-taking at their proximity.

"Oh! Am I uh... am I interrupting something?" he asked, eyes darting between the two of them nervously.

Sonic did his best to laugh it off, pushing down the strange fluttering that had occupied his stomach all of a sudden. "Nah, I think he's just worried, is all."

"That makes two of us," Tails said, leaning against the door jamb. "Speaking of, I'd like to do a few tests to try and determine the extent of Shadow's... condition. If that's okay?" He looked to the hedgehog in question.

Very little about Shadow's expression changed, but his ears flattened.

"Hey," Sonic nudged him with an elbow. His attention slid easily back to him once more. "He's not gonna do anything to hurt you, you know. We just want to figure out what's going on." He pitched his voice a little lower. "I know you're not a huge fan of doctors, but I promise Tails is good -- he's been patching me up for years now. And if you still don't want any part in it, we won't force you." He smiled encouragingly. "What do you say?"

There was a moment's pause, and then slowly, Shadow nodded.

"Well, he seems to understand what's going on just fine," Tails remarked, finally leaving the doorway. He handed a sheet of tablets and a cold-pack to Sonic. "Keep that on your eye for twenty minutes," he instructed before turning to his next patient. He lifted a hand, index raised. "Follow my finger with just your eyes, okay?"

Sonic sat back and watched with one good eye and no small amount of amusement as Tails performed his "tests". It was a bizarre combination of Sonic's own examination for his concussion and a field sobriety test. Questions ranged anywhere from, "Are you experiencing any pain?" to, "Have you taken any substances within the last twenty-four hours that may impair your judgement?"

"You mean besides the obvious?" Sonic joked and got an eye-roll from Tails for his trouble.

Shadow answered to the best of his ability and complied with all of Tails' polite requests to follow his finger, and so on and so forth.

The first surprise came when Tails shone a mini flashlight into Shadow's eyes. He squinted automatically at the direct light, but even Sonic could see that his pupils had stayed dilated.

Tails took a step back. "That's a little concerning."

"What does that mean?" Sonic asked, leaning forward, elbows propped up on his knees. The ice-pack lay to one side, momentarily forgotten. He didn't know that much about medicine, but what little he _did_ know… "Could the serum have caused some kind of head trauma?"

"Not necessarily," Tails answered, clicking the flashlight off and setting it to one side. He made a quick note on his computer before turning back to where Shadow sat on his workbench. "There are a number of drugs that can have this effect -- both medicinal and recreational. It's possible that the serum is behaving similarly."

It wasn't the best reassurance, but considering that Shadow showed few other signs of head trauma, they could safely rule it out. His balance and coordination remained perfectly intact.

The next surprise happened after checking his vital signs. Listening to Shadow's heart rate revealed no abnormalities; though Tails noted down his feverish temperature with a mutter of, _"Better keep an eye on that."_ But then-

"Say 'ah', please," Tails told him, wielding a popsicle stick as a tongue depressor. He gently pressed down on Shadow's tongue, exposing the inner cavern of his mouth and throat. Craning to get a good look, Tails applied more pressure. Shadow's canines _flexed._

Both Sonic and Tails startled.

"Holy _crap,"_ Sonic exclaimed. "Has he always been able to do that?" 

"Fascinating! There must be a mechanism in his upper jaw that allows them to protract and retract. I wonder what their full range of motion is," Tails mused aloud.

To his delight, Shadow kept his mouth open, allowing them to watch as he wiggled his fangs, teeth lengthening and shortening at will. It almost looked like he was showing off.

Sonic grinned. That was _so_ cute. He hoped Shadow would be returned to normal soon; he couldn't wait to tease him about this.

Finally tossing the popsicle stick in the bin, Tails concluded, "His throat looks fine, so I'm pretty sure his speech-block is psychological rather than physical." He brought a hand to his chin. "But it's strange. If the cause was damage to the language-processing part of his brain, then he shouldn't be able to understand us, either."

Sonic shrugged, feeling clueless. "Maybe it only affects some functions but not others?"

Tails hummed in response, clearly deep in thought. Sonic could practically hear the gears turning in that big brain of his. After a moment, he turned back to Shadow.

"Alright, I have one more test I'd like to perform," Tails announced, stepping around their make-shift exam table to rummage through a drawer. "I know I've asked a lot of you already, but this should be the last one."

"Is that okay, bud?" Sonic checked with him. Shadow nodded.

Tails turned back to them. "Okay, for this test I just want you to focus on me."

He walked towards Shadow, one slow step at a time. Sonic watched him curiously. He couldn't think of what kind of test this could be that they hadn't already covered in the last hour. His suspicion only grew when he noticed that, despite searching for something moments ago, Tails' hands were empty.

Sonic's eyes widened in realization just as Tails came to a stop.

_"Think fast!"_

He twisted, tails whipping through the air, launching the stress toy held within their grip to Shadow's right.

It was a fastball, but Sonic could tell right away it wasn't even close to his rival's speed. This was going to be a piece of cake for him.

Except, instead of catching it in one hand like he'd expected, Shadow _pounced,_ lunging for the stress toy and pinning it to the floor with his claws. He growled. It sounded smug.

Sonic gaped. Meanwhile, Tails was slowly nodding his head, as if Shadow turning feral was just an everyday occurrence.

"What the heck was _that_ all about?"

"I've got a pretty good idea of what we're dealing with now," Tails said, recording the results. "Do you remember what Dr. Eggman said about the serum?"

"Something about amplifying emotions and stopping Shadow's impulse control," he recalled. Shaking his head, he continued. "But it didn't work. He said Shadow was supposed to attack me, not... do whatever _this_ is."

"It didn't work the way Eggman _intended,"_ Tails corrected him.

Sonic looked at Shadow, still crouched on the garage floor, watching them curiously, then back at Tails.

"Think of it like this: your behaviour is a combination of your impulses and your higher reasoning. If you were to find a fresh chilli-dog lying around, your first impulse would be to eat the whole thing in one go, right?"

"You make me sound like a glutton," Sonic complained. Tails summarily ignored him.

"But your _higher reasoning_ might tell you it'd be a better idea to save it for later, or share it with a friend. Normally, the two balance each other out, but under certain circumstances, the brain will shut down its higher-reasoning in favour of its impulses --" 

"Like in fight-or-flight mode," Sonic realized.

Tails looked indescribably pleased by this. "Exactly! But that's an extreme case, where your brain is solely focused on ensuring your own survival. It'll understand the world purely by distinguishing between threats and non-threats." He clapped his hands together. "So! Here's my hypothesis: Dr. Eggman _intended_ to induce a fight-or-flight response in Shadow, hoping that he would attack you. _Instead,_ the serum has inhibited Shadow's higher reasoning to some extent -- which we can see from his behaviour and his difficulty speaking -- but not enough to keep him stuck in survival mode." Tails grinned devilishly. "Which means he _failed."_

As Tails started clearing things away, Sonic shifted antaily in his seat. "There's something I still don't get. So, Eggman was trying to send Shadow into full berserker-mode, fine." He shook his head. Even just saying it aloud, it sounded ridiculous. "But even if it'd worked -- and that's a pretty darn big _if_ \-- it doesn't exactly equal world domination all on its own."

Tails snorted. "I'm surprised -- Eggman didn't lay out his entire scheme and all its steps in his monologue?"

"Not this time," Sonic said wryly. It was anyone's say whether it was a blessing or a curse. Eggman hadn't gone on for long enough to bore him to death, but it left them with little idea of the scope of his plans. Sonic stared at his shoes and thought back, trying to pick out any details that might give his nemesis away. After a moment, it came to him.

"A broadcast," Sonic said suddenly, catching Tails and Shadow's attention again. Looking to his little brother, he explained, "Eggman said he was gonna film my "grand defeat" and show it off to everyone. Did you catch any wind of that?"

Tails flashed him a smile. "Nope, but that's _definitely_ a lead I can follow up on. You just leave it to me."

"So, what happens now?" Sonic asked. His mind returned to their current situation. "Is there a way to reverse the serum's effects?"

Tails ducked his head, one hand rubbing the back of his neck. "I don't know, Sonic. You know biochemistry isn't really my strong suit."

Sonic scoffed. "Nonsense. There's nothing I've ever seen that you haven't been able to pick up in less than a week." He slung an arm around his shoulders, tugging him into a one-sided hug. "You're the smartest person I know, Tails. I know you can do it."

"Aw, shut up," he mumbled, embarrassed, but his tails were wagging happily.

They enjoyed the hug in a moment of content silence before Tails spoke up.

"Actually," he began, pulling away. "If I want to figure out what exactly the serum is made up of, I'll need to take a blood sample."

Out of the corner of his eye, he caught Shadow -- who had been idly toying with the stress ball -- going dead still. Sonic turned to him, frowning at the way he was staring wide-eyed, his gaze fixed unwaveringly on Tails.

"Shadow?"

Oblivious to the sudden change, Tails continued muttering to himself. "Now, if I could just find that -- there it is!"

From the first aid kit, Tails pulled a syringe, its sharp tip glinting in the lamp light.

Shadow's reaction was immediate. His lips pulled back in a grating snarl, quills bristling, teeth bared defensively. He looked ready to _maul_ someone. And all the while, those dark eyes never left the needle in Tails' hand.

It was empty, of course. There were no mind-altering drugs for Tails to force upon him, but Sonic knew that wouldn't matter to Shadow.

Heedless of his own injuries, Sonic threw himself between the two of them. He spread his arms wide, blocking Shadow's view of Tails. It was crucial that he de-escalate the situation _now,_ before it could spiral out of control.

_And if worse comes to worst,_ a cynical voice whispered in the back of his mind, _I'd rather take the hit than let him lay even a finger on Tails._

Shadow's focus snapped to him. He shifted uneasily, like he couldn't decide whether to run or stand his ground. As if Tails and Sonic were a threat to him. The idea pained Sonic to think about it.

"We won't force you," he told Shadow.

The noise quieted, until there was nothing but a heavy silence in the garage. Shadow's eyes were still on him -- watching, waiting -- but they were far away. As if he was seeing something else entirely.

"You remember what I said earlier? About these tests?" He took a step towards him, aching to close the gap. Shadow noticed this and tensed. Sonic kept talking, keeping his voice gentle and reassuring, trying to get through to him. "We don't want to hurt you, and we don't want to make you do anything _you_ don't want." Another step closer. It didn't feel like Shadow was staring right through him anymore. "If this is you saying no, then we won't do it. Simple as that."

Sonic stopped in front of him and slowly lowered himself to the ground. They were face to face now.

"Tails," he said without turning back. "Can you find a way to reverse it without the sample?"

Tails' answer came after a moment, tone apologetic. "...It would take me a lot longer. Without it, I wouldn't know what specific measures to take in order to counteract the effects of the serum -- and brain chemistry is a delicate science."

The two of them stayed there, ignoring the discomfort of the cold hard ground, eyes searching each other. Sonic wondered what Shadow found in him. All _he_ could see was the lab table, Shadow bound and gagged against his will. The memories came flooding back, as easily as rewinding a roll of film. He remembered how terrified Shadow had looked then, how helpless he had been to stop it. He remembered the echo of Eggman's words.

_"Think of how much this will_ help _you."_

It was an impossible choice in front of him -- try to force help on someone who adamantly didn't want it, or sit back and just _let_ the serum do its worst to one of his friends. There was no way Sonic would allow the latter. But he _hated_ the idea of betraying Shadow's trust like that. He didn't want to become just like everyone else who had ever hurt Shadow, who had made him believe that he couldn't count on anyone but himself.

Sonic squeezed his eyes shut. His hands balled into fists so tight they shook, blunt claws biting into his palms. He wanted to tear through a hundred Eggbots, run a thousand miles -- something, _anything_ \-- but the indecision left him paralyzed. Even if he did force it and got his friend back to normal, it wouldn't matter how much he tried to justify his actions to Shadow, to himself. It was still _wrong._

_I won't put him through that. Not again._

He felt fingers rest over his wrist, and his shaking hands fell still.

"Sonic."

The voice was rough, the sounds almost unrecognizable. But Sonic would know that voice anywhere.

He looked up.

Shadow met his gaze evenly. His spine was straighter, carrying himself with dignity, instead of hunched over like a hunter ready to pounce. There was a defiant tilt to his chin, practically _daring_ Sonic to argue with him.

"You... help?"

Each word sounded as if it'd been forced out, but there they were, all the same.

Sonic nodded.

Shadow's head cocked to one side, looking past him to where Tails no doubt stood, equally stunned.

"Do it."

Sonic wondered if he was imagining it when, for a split-second, the fire returned to Shadow's eyes.

* * *

It still wasn't easy.

Shadow remained stubbornly silent as Tails prepped him. The thin fur on the inside of his elbow was delicately shaved off, the site cleaned and disinfected. A tourniquet was applied to his upper arm. Tails quietly asked him to make a fist. And still, not a peep left him.

It was like he was trying to prove something to them. He _had_ asked to go through with this, after all.

But try as he might, Shadow couldn't hide his discomfort from him. Not when he was squeezing the life out of Sonic's hand.

"You're doing great," Sonic assured him. "It'll be over before you know it."

"Ready?"

"I think we're as ready as we'll ever be," he said with a glance towards Shadow, his expression unchanged.

"Okay, I'm gonna count down now. 3... 2... 1..."

The needle slid in with no resistance. Shadow tensed up, hissing his displeasure. Sonic squeezed his hand, rubbing a thumb over his knuckles in hopes to distract Shadow from the sensation. He kept muttering reassurances, only half aware of what he was saying.

"I know, bud, I know. It's okay. You're being really brave, right now."

"And done!" Tails announced, withdrawing the syringe and immediately covering the puncture site with a pad of gauze. "Sonic, can you apply pressure on his arm while I put this away? It'll help the blood clot faster."

"Sure thing." He shifted to Shadow's other side easily, taking the gauze from his little brother and doing just as instructed.

Tails wandered away from them. Most likely, he would spend the next few minutes sorting out the sample so it would be ready for analysis. He glanced up at Shadow. His expression remained disgruntled.

"I'm really proud of you, you know," Sonic said softly.

Shadow cocked his head, brow raised in confusion. Sonic chuckled.

"It's true!" he insisted. His gaze fell to his hands on the gauze, thumb still rubbing back and forth absent-mindedly. "It's like no matter how much the world gets you down, you always find a way to keep on kicking." He met Shadow's eyes and his breath caught. 

There was that look on his face again. The one that almost felt like a physical touch. He swallowed.

"You're amazing."

The words came out as a murmur, but he knew Shadow had heard him. He leaned in, close enough to feel the warmth radiating off him -- but before Sonic could panic or even muster up the sense to be confused over the sudden twisting in his stomach -- Shadow gently bumped their foreheads together. It reminded him of a sleepy Tails back in his younger days, clumsy but sincere with his affection.

He blinked.

"Uh... Thanks?"

Shadow blinked back at him. He seemed pleased.

Trying to shake off the strange feelings, Sonic called over his shoulder, "Hey Tails, you got everything you need now?"

"Yup! That's all for today."

Sonic didn't think it was exaggerating to say they _all_ sighed in relief at that.

**Notes for the Chapter:**

> As a disclaimer, I feel I should say that if you or a loved one receive a head injury or are drugged with some unknown substance, you should ABSOLUTELY go to the hospital. Unfortunately for Tails, he's stuck with arguably the two worst characters to try and convince to see a doctor. Poor guy, he's doing the best he can.
> 
> Thanks so much for reading! Feel free to let me know what you think in the comments <3

**Author's Note:**

> Thank you so much for reading! I've been working on this story for quite a while and I'm happy to be able to share it. Please let me know what you think in the comments! The feedback is greatly appreciated.


End file.
